Protein kinase Cδ mediates cyclic adenosine monophosphate–stimulated translocation of sodium taurocholate cotransporting polypeptide and multidrug resistant associated protein 2 in rat hepatocytes
✍ Scribed by Christopher M. Schonhoff; Henry Gillin; Cynthia R. L. Webster; M. Sawkat Anwer
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- English
- Weight
- 522 KB
- Volume
- 47
- Category
- Article
- ISSN
- 0270-9139
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✦ Synopsis
Cyclic adenosine monophosphate (cAMP) stimulates translocation of Na ؉ -taurocholate (TC) cotransporting polypeptide (Ntcp) and multidrug resistant associated protein 2 (Mrp2) to the plasma membrane. Because cAMP activates phosphoinositide-3-kinase (PI3K) and protein kinase C (PKC) activation is PI3K-dependent, the aim of the current study was to determine whether cAMP activates conventional and novel PKCs in hepatocytes and whether such activation plays a role in cAMP-stimulated Ntcp and Mrp2 translocation. The effect of cAMP on PKCs, TC uptake, and Ntcp and Mrp2 translocation was studied in isolated rat hepatocytes using a cell-permeable cAMP analog, CPT-cAMP. The activity of PKCs was assessed from membrane translocation of individual PKCs, and phospho-specific antibodies were used to determine PKC␦ phosphorylation. TC uptake was determined from time-dependent uptake of 14 C-TC, and a cell surface biotinylation method was used to determine Ntcp and Mrp2 translocation. CPT-cAMP stimulated nPKC␦ but not cPKC␣ or nPKC⑀, and induced PI3K-dependent phosphorylation of nPKC␦ at Thr 505 . Rottlerin, an inhibitor of nPKC␦, inhibited cAMP-induced nPKC␦ translocation, TC uptake, and Ntcp and Mrp2 translocation. Bistratene A, an activator of nPKC␦, stimulated nPKC␦ translocation, TC uptake, and Ntcp and Mrp2 translocation. The effects of cAMP and bistratene A on TC uptake and Ntcp and Mrp2 translocation were not additive. Conclusion: These results suggest that cAMP stimulates Ntcp and Mrp2 translocation, at least in part, by activating nPKC␦ via PI3K-dependent phosphorylation at Thr 505 .